Hydrilla: coming to a pond near you?

August 23, 2011

August is here and it seems that a report of a new invasive species appears nearly every week. It happened last summer and it's happening this summer, too. Last week I read about Asian clams in Lake George, feral hogs in Washington County and now hydrilla in the Finger Lakes. It's enough to make one throw up one's hands in exasperation and shout, "What's the point!" But, don't despair. Take a deep breath, stay focused and keep going - that's what I'm doing, and many others are, too. We simply cannot give up. We finally have solutions and many of them are right at our fingertips.

Invasive plants are easier to detect and control than invasive animals, which move easily on their own around the landscape or waterways. We have a real shot at controlling invasive plant expansion, but we need to be vigilant in preventing introductions, detecting new infestations early and responding rapidly with appropriate measures.

Many shoreowners and paddlers are familiar with Eurasian watermilfoil, but other invasive aquatic plants are also on the move. It is important to learn to identify the invasive plants at our doorstep because if we focus on only one, we may get blindsided by another.

Article Photos

Hydrilla Whorl(Photo— Robert Videki, Doronicum Kft., Bugwood.org)

Side view of Hydrilla Whorl(Photo— Robert Videki, Doronicum Kft., Bugwood.org)

Hydrilla, for instance, is a relatively new invader on the New York invasive scene, though it's one many have warned against. It is considered by many aquatic specialists as the most problematic aquatic plant in the U.S. and plagues waterways in California and the northwest, from Texas to Pennsylvania and in recent years in New York and New England. Control costs soar into the millions.

Hydrilla made its way to the U.S. from Africa, Australia and Asia through the aquarium trade during the mid-1900s. Unsuspecting aquarium owners may have dumped unwanted plants into a nearby lake, fragments may have hitched a ride on watercraft or, in some cases, tubers may have stowed away on other aquatic plants, like water lilies, shipped from far away places for water gardens.

In New York, shoreowners first detected hydrilla in 2008 in a private pond in Orange County. Surveys later that summer revealed it was also in several ponds on Long Island. The detection of a new species in the state rightly triggered a swift response involving the town, shoreowners and the State Department of Environmental Conservation to eradicate the infestation. Management efforts are still underway.

Unfortunately, last week, lake users identified another hydrilla infestation in the inlet to Cayuga Lake in the Finger Lakes region, which is at least 150 miles from the closest known infestation in the Hudson Valley. Fortunately, a response plan is now being developed.

Stamping out these infestations is a must. Each hydrilla infestation left unmanaged is a source for many others. We cannot afford to let hydrilla become the next Eurasian watermilfoil - the most widespread aquatic invasive plant.

Hydrilla is often referred to as the Godzilla of aquatic invading plants. Its quick and thick growth - up to 1 inch a day - crowds out beneficial native plants, degrades habitat for fish and wildlife and impairs boating, fishing and swimming. It grows to depths of 30 feet and tolerates varying nutrients, light, pH and sediments. Dense infestations can also clog irrigation and flood-control canals. Major infestations limit sportfish weight and size due to the plant's ability to alter water chemistry and oxygen levels.

Like other invasive plants, hydrilla reproduces in several ways, giving it a competitive edge over natives. It spreads by seeds or sprouts new plants from root fragments or stem fragments. It also produces tubers and turions, small reproductive structures that settle into sediments enabling it to effectively withstand ice cover, drying, herbicides and ingestion and regurgitation by waterfowl.

Hydrilla looks similar to native waterweed, Elodea, but can be distinguished by its five to six leaves in whorls around the stem (Elodea has three) and serrations or small spines along the leaf edges (Elodea's edges are smooth).

There are simple steps to help prevent the spread of hydrilla and other aquatic invaders: Clean recreational gear after each use. Inspect purchased plants for hitchhikers. Never release aquaria plants or animals into the wild. Learn to identify the invaders here and those that may be on their way and report suspect sightings to APIPP at 518-576-2082.

---

Eye on Invasives is a biweekly column that spotlights a top invader when it is easiest to identify. Hilary Smith directs the Adirondack Park Invasive Plant Program, a partnership program housed at the Adirondack Chapter of The Nature Conservancy in Keene Valley. Find out more about this award-winning program online at www.adkinvasives.com.